1. Technical Field
The present disclosure relates to equipment for aligning liquid crystals (referred to as aligning equipment), and more particularly to aligning equipment that transports substrates along various routes.
2. Discussion of Related Art
In general, liquid crystal has electrical properties that cause changes in alignment of the liquid crystal when an electric field is applied, and optical properties that cause variations in light transmittance in accordance with the alignment of the liquid crystal. A liquid crystal display (LCD) device takes advantage of the electrical and optical properties of liquid crystal to display an image.
An LCD device is divided into a liquid crystal controlling part and a light providing part. The liquid crystal controlling part controls alignment of the liquid crystal to display an image, and the light providing part supplies light required to display an image to the liquid crystal controlling part.
The liquid crystal controlling part may have various structures depending on the type of liquid crystal. A twisted nematic (TN) mode LCD device using a TN mode liquid crystal, for example, includes a first substrate, the TN mode liquid crystal and a second substrate. The first substrate includes a first electrode, and a first alignment layer covering the first electrode. A first alignment groove extending in a first direction is formed on the first alignment layer. The second substrate includes a second electrode facing the first electrode, and a second alignment layer covering the second electrode. A second alignment groove extending in a second direction is formed on the second electrode.
LCD devices can also use a vertical alignment mode liquid crystal (VA mode LC). Examples of such devices include a vertical alignment (VA) mode LCD device and an in-plane switching (IPS) mode LCD device.
An optical controlled birefringence (OCB) mode LCD device includes a first substrate, an OCB mode liquid crystal and a second substrate. The first substrate includes a first electrode and a first alignment layer formed on the first electrode. The second substrate includes a second electrode facing the first electrode and a second alignment layer formed on the second electrode.
The OCB mode LCD device forms an alignment groove that extends in a direction substantially identical to that of the first and second alignment layers.
The IPS mode LCD device includes a first substrate, a VA mode LC and a second substrate. The first substrate includes a first electrode, a second electrode disposed on the first substrate and a first alignment layer covering the first and second electrodes. An alignment groove is formed on the first alignment layer. The second substrate faces the first substrate, and a second alignment layer is formed on the second substrate. The VA mode LC is interposed between the first and second substrates.
The VA mode LCD device includes a first substrate, a VA mode LC and a second substrate. The first substrate includes a first electrode and a first alignment layer formed on the first electrode. The second substrate includes a second electrode facing the first electrode and a second alignment layer formed on the second electrode. The VA mode LCD device includes a groove or protrusion on the first and second electrodes to align the VA mode LC. Thus, an alignment groove for aligning liquid crystal on the first and second alignment layers is not required in the VA mode LCD device.
Both first and second substrates of the TN mode LCD device, the OCB mode LCD device, the IPS mode LCD device and the VA mode LCD device as described above include an alignment layer. The first or second substrate of the TN mode LCD device, the OCB mode LCD device, the IPS mode LCD device and the VA mode LCD device is loaded in a consolidation state into aligning equipment so that an alignment layer can be formed on the first or second substrate.
Most conventional aligning equipment includes an alignment layer-forming device that forms an alignment layer and an alignment groove-forming device that forms an alignment groove. The alignment layer forming device and the alignment groove-forming device are disposed in an in-line manner, so that the aligning equipment may successively perform processes for forming the alignment layer and for forming the alignment groove on the alignment layer. After the alignment layer-forming device forms an alignment layer on the first and second substrates, the LCD device is transported to the alignment groove-forming device where the alignment groove is formed on the alignment layer.
An alignment groove is not formed on the alignment layer of a VA mode LCD device. Hence, the first and second substrates of the VA mode LCD device directly pass through the alignment groove forming device or an auto guide vehicle (AGV), and then are transported to a subsequent process.
When the first and second substrates of the VA mode LCD device pass through the alignment groove forming device, the first and second substrates also pass through various kinds of units disposed within the alignment groove forming device, such as, for example, a cleaning unit, an alignment unit, a rubbing unit, a rinsing unit, etc., in sequence. Thus, the alignment groove forming process for the TN LCD device, the OCB mode LCD device and the
IPS mode LCD device may be delayed while the VA mode LCD device passes through the units.
Additionally, when the first and second substrates are transported by a separate AGV, the total area of the aligning equipment increases due to the space occupied by the AGV. Further, installation and control of the AGV is expensive.
When the AGV transports the VA mode LCD device using a transporting cassette, the AGV needs to be on standby until the transporting cassette is filled with the VA mode LCD devices. Thus, the VA mode LCD device is exposed to the atmosphere for a long period while the transporting cassette is loaded. Consequently, various particles such as dust may attach to the alignment layer of the VA mode LCD device, thereby requiring rinsing of the VA mode LCD device before proceeding with the next process.
Each of the TN mode LCD device, the OCB mode LCD device, the IPS mode LCD device and the VA mode LCD device should have its own alignment layer forming device. However, this would require relatively expensive aligning equipment that occupies a large area.